1. Field of the Invention
This invention relates to apparatus for connecting and disconnecting joints of pipe, particularly pipe joints in a string of pipe in an offshore location.
2. Description of the Prior Art
In the drilling of offshore oil and gas wells it is necessary to sink large pipes into the subsea bottom, such pipes consisting of a number of joints of pipe connected together end to end. For example, such pipes may consist of a conductor casing which is drilled, driven or jetted into the sea floor a substantial distance, and which has connected to its upper end and extending upwardly to an above-water platform or floating vessel a conductor riser which constitues a large diameter pipe through which drilling operations are performed.
In addition, the support legs of offshore platforms from which drilling operations are performed often consist of pipe through which hollow steel pilings are driven or drilled into the sea bed.
Each of such pipes have been connected by various means in the past, including ordinary screw threads, welding, clamps, and a special type of breech block connection such as is shown, for example, in U.S. Patent Application Ser. No. 103,839, filed Jan. 4, 1971, now U.S. Pat. No. 3,800,869 which is assigned to the assignee of the present application.
In making up the aforesaid strings of pipe, a first joint of pipe is lowered from a platform or vessel and following joints of pipe are connected in sequence above it. As each connection is made, the string of pipe is lowered until it sinks down into the sea bottom and the drilling, driving or jetting operation is then performed to sink the string deeper into the sea bottom, with additional joints of pipe being added as necessary. Because of many advantages found therein, the breech block connector, as, for example, of the type described in the aforesaid patent application Serial No. 103,839 has been found to be particularly advantageous. Such connections are made up at the surface and the connection is secured by a latch to prevent any possibility of the connection being released at an underwater or underground location.
However, in some instances it is necessary to disconnect a joint in a string of such pipe. For example, in the case of the conductor casing for an oil well, the conductor riser may be disconnected after the well is completed, since it is not needed thereafter. In the past it has been necessary to stop all operations on the platform and send a diver down to release the latch so that the joint may be disconnected. This has been a very undersirable and expensive practice, because no operations can be performed while the diver is under water, and the operation may take several hours in many cases. Furthermore, where the water is extremely deep or cold, or there is a high current flowing, or the connection to be released is buried in the mud, it is difficult if not impossible for a diver to release it.